Oncogenes appear to be involved in several kinds of cancer in animals and man. An understanding of their function(s) and their alterations in neoplasia is still required. Toward this goal, we are studying the oncogenes present in MC29 and MH2 viruses following genetic, biochemical and physiological approaches. Deletion mutants of the mht and myc oncogenes have been constructed (see Project Number Z01CE05239-03 LMO) and their transformation efficiency is measured in transfection assays. The role of different portions of these oncogenes in transformation can, therefore, be assessed and correlated with the expression of truncated, oncogenerelated proteins. Such proteins have been identified in transformed/transfected cells by using specific antibodies. Similar antibodies enable us to immunoprecipitate the cellular counterparts of viral oncogenes in normal or in malignant cells. A more physiological characterization of the myc oncogene is also obtained, taking advantage of the known DNA binding properties of the myc protein. Different DNA's are utilized in order to measure specific and/or non-specific binding of the myc protein. The possible role of oncogenes and protooncogene abnormalities in non-virally-induced cancers has also been studied in human neuroblastoma and mouse lymphoma.